Galestro is a soil type described by Tom Stevenson (2011, p.18) as a rocky, schistous clay soil commonly found in most of Tuscany’s best vineyards.’ Enzo Tiezzi (of the Tiezzi winery in Montalcino) told me (9th April 2015) galestro is a rock formation of stone (mudstone or clay but not compact clay) and sand which will become clay, but has not yet reached the full clay stage. Others call galestro a clay-based shale, a friable shale, and sandstone slate. The Oxford Companion to Wine (2015, p.304) describes Galestro as the ‘Italian name for the friable rock of the marl-like soil that characterizes many of the best vineyard sites in Chianti Classico.’
Ian D’Agata (2019, p.277-8) defines galestro as ‘highly friable (unlike alberese), a metamorphic medium-grained clay schist made of flaky layers (what geologists describe as “foliated”). Though often said to be “shaley” (schist and shale are related), true galestro is more schistous than shaley; galestrino is the term that ought to be used to describe Chianti’s finer-grained, shale-like soils.’
Sebastiano Capponi of Villa Calcinaia in Greve in Chianti describes galestro as ‘a clayey schist whose exfoliating structure, crumbly surface, permeability, pebble content and wealth of trace elements ensure the vine’s vegetative balance and characterful wines.’
Rodolfo ‘Rudy’ Cosimi of Il Poggiolo in Montalcino says ‘stones called galestro are very crumbly and flake easily under the action of rain and sun, thus releasing many minerals as nourishment. A sedimentary soil, galestro drains well, avoiding water stagnation at the plant root level, whilst retaining sufficient moisture for the vines and their grapes. You get fluid, textured wines which do not need to muck oak.’
Jan Erbach of Pian dell’Orino in Montalcino told me ‘galestro is another type of calcaric sediment and is like schist. The schist in Montalcino was created in a very deep sea which is now the Mediterranean (Formation ligure-P). As this sea was so deep it had cool temperatures. There greater pressure at these depths means there was less marine life and only a very slow sedimentation of the calcareous particles. The base of the sea was a layer of magma, with the sediments on top in this very deep sea. Then the sea emerged as did the galestro which has a slatey appearance. Galestro can decompose easily, so even though it is outwardly hard it is not compact or unyielding. It breaks into little pieces, and so helps aerate soil. Galestro is rich in cations. This allows the vine roots to secrete hydrogen ions, and in return via transpiration they receive sodium and magnesium. It needs these minerals to make leaves, photo-synthesise and create sugars to build the potassium they need to create cells. Galestro is a wonderful soil for vines.’ See also Castelgiocondo in Montalcino.
Wine style: As galestro is able to hold water, it allows Sangiovese to ripen without suffering heat stress in areas like Montalcino and Chianti Classico. Sangiovese from galestro gives darker, richer wines compared to alberese, Séan O’Callaghan told me.
Bill Nesto MW & Frances Di Savino, Chianti Classico, the Search for Tuscany’s Noblest Wine, (University of California Press, 2016).
Dr Ian d’Agata, Native Wine Grape Terroirs (University of California Press, 2019).
Oxford Companion to Wine 4th edition ed. Jancis Robinson MW and Julia Harding MW (Oxford University Press, 2015.
Tom Stevenson (2011) The Sotheby’s Wine Encyclopedia 5th Edition by Tom Stevenson (Dorling Kindersley, 2011).